The present invention relates to magnetic sensors and, particularly, to a flux-gate magnetic sensor for use in a vehicle.
Compasses for vehicles such as automobiles, typically, are after-market items of a relatively basic mechanical design. Such compasses, typically, attach to the dashboard of the vehicle and are of inexpensive construction including a compass card suspended by a pin bearing and mounted within a housing. Usually, they will include some elemental form of adjustment or compensation mechanism such as movable magents for adjusting the compass to north and south, depending on the geographical area of use of the vehicle.
The theory of operation of flux-gate magnetic sensors is well known and one application to the automotive environment is described in an article entitled "Magnetic Field Sensor and its Application to Automobiles" by Hisatsugu Itoh published on Feb. 25-29, 1980 by the Society of Automotive Engineers, Inc. as SAE Technical Paper No. 800123. The positioning of such a sensor in a vehicle is very important since the transitory magnetic fields produced by the vehicle's electrical system, as well as the ferrous material of the vehicle itself can adversly affect the operation and reliability of a compass employing such a sensor.
With the many magnetic fields surrounding the dashboard area of a vehicle, many of which are transitory in nature depending upon the operation of the vehicle and its accessories, the dashboard area is a poor location for magnetic sensors including a flux-gate sensor. Experimentation has resulted in the discovery that placement of a sensor such as a flux-gate sensor in the upper center windshield area of a vehicle provides an unexpectedly stable and reproducible environment for a magnetic sensor.